I built a ‘crystal’ set when I was about 12. Used a cheap ear piece, salvaged tuning capacitor and wound the coil on a toilet roll (varnished it to keep it in place) plus an arrangement to pick off the coil to adjust L. I salvaged a few OA81 germanium diodes for the ‘detector’ from some old transistor radios.
Worked very well except all the stations came in at the same place ie no tuning whatsoever.
I only learned a few yrs later that the problem was that the earpiece was probably loading the tank circuit and it would have worked better with a buffer after the detector.
Another project for the grandson if he is so inclined when he’s a bit older.
Worked very well except all the stations came in at the same place ie no tuning whatsoever.
I only learned a few yrs later that the problem was that the earpiece was probably loading the tank circuit and it would have worked better with a buffer after the detector.
Another project for the grandson if he is so inclined when he’s a bit older.
Whatever happened to Germanium transistors? Lower bias than Silicon's 0.7V, weren't they? 🙂
https://www.bbc.co.uk/bitesize/articles/zbcf8xs#xtor=CS8-1000-[Discovery_Cards]-[Multi_Site]-[GR05]-[PS_BITESIZE~N~~A_SolarSystemQuiz]
Question 2 of 7:
Which of our dwarf planets is not a 'plutoid'?
Ceres
Makemake
Haumea
Geranium
I fluked it. Had no idea what a Plutoid was. 😱
https://www.bbc.co.uk/bitesize/articles/zbcf8xs#xtor=CS8-1000-[Discovery_Cards]-[Multi_Site]-[GR05]-[PS_BITESIZE~N~~A_SolarSystemQuiz]
Question 2 of 7:
Which of our dwarf planets is not a 'plutoid'?
Ceres
Makemake
Haumea
Geranium
I fluked it. Had no idea what a Plutoid was. 😱
My father helped me build a crystal set when I was a boy.
He used a proper 'cat's whisker' to rectify the signal. This consisted of a crystal of galena which you had to probe with a fine wire until you found the sweet spot for rectification.
The single headphone unit was a high impedance WW2 surplus job. As you discovered, Bonsai, low impedance types are no good for this application.
What is essential with a crystal set is a good earth and an extremely long length of wire, strung right across the garden, to act as an aerial.
The selectivity (the ability to distinguish one radio staion from another) was sufficient to pick out Radio Luxembourg at night, when I would listen to the latest pop tunes in my bedroom.
I went on to build many crystal sets in later life and was always amazed as to how much volume you could get from the headphones considering there were no batteries in the radio circuit - all the energy comes from the radio waves themselves.
P.S. Knowing of my interests, a well meaning friend bought me a Radio Receiver Kit - "Make a Crystal Radio Just Like Grandad Made".
It cost him £25.99 and I hadn't the heart to tell him he'd purchased what was basically a few bits of MDF, a coil of wire, a diode and a crystal earpiece - worth about 50p in total! It didn't even have a tuning capacitor, being the most basic circuit imaginable.
I wouldn't consider wasting my time building it as I know it would be rubbish, and it's now lined up for going to the charity shop!
Attachments
Bonsai was talking about germanium diodes which have a forward voltage drop of around 0.3 V.
This results in them having a low power loss, making for an efficient diode
However, there are several practical reasons why silicon diodes are preferred over germanium.
One is that the crystal structure of germanium gets destroyed by high temperatures whereas silicon crystals are not easily damaged by excess heat.
Also silicon (basically sand) is more abundant and therefore cheaper than germanium.
Last edited:
I have tended to forget a lot of stuff over the years... I was mostly an Antenna Man back in the day. Strictly 50 and 75 Ohms. With so much NEW STUFF to take in, gotta make ROOM somewhere. 😀
I would think that earpiece of yours is Piezo. Those old headphones and telephone headsets were a coil and a permanent magnet close to a magnetic steel diaphragm. Very efficient.
The Science Museum in South Kensington might like that thing of yours. They have a big display of retro technology on the Computer floor. Amazing old gadgets and toys that us oldies remember from when they were new and exciting.
I just checked, and Long Wave Radio Luxembourg 208 (RTL) was 1300kW of power on AM. Government hated the idea of "the youth" listening to unapproved music. Shut down all the pirate stations, and recruited their "Disk Jockeys" like Tony Blackburn and Simon Dee.
The Long Wave was around 153-281 kHz. 3-6 kHz modulation and that's 20-40 long distance stations on a clear day or night. 300-3000 Hz was considered ample to hear voices well.
RTE (Ireland) is still at 252kHz. Radio 4 still broadcasts at 198kHz , and incidentally sends a sideband that controls Britain's electricity meters. Don't tell the Russians! Terrible quality. Must need a huge aerial really.
Mustn't go on. Just had a listen to Thomas Dolby "The Golden Age of Wireless". Still sounds fresh.
I would think that earpiece of yours is Piezo. Those old headphones and telephone headsets were a coil and a permanent magnet close to a magnetic steel diaphragm. Very efficient.
The Science Museum in South Kensington might like that thing of yours. They have a big display of retro technology on the Computer floor. Amazing old gadgets and toys that us oldies remember from when they were new and exciting.
I just checked, and Long Wave Radio Luxembourg 208 (RTL) was 1300kW of power on AM. Government hated the idea of "the youth" listening to unapproved music. Shut down all the pirate stations, and recruited their "Disk Jockeys" like Tony Blackburn and Simon Dee.
The Long Wave was around 153-281 kHz. 3-6 kHz modulation and that's 20-40 long distance stations on a clear day or night. 300-3000 Hz was considered ample to hear voices well.
RTE (Ireland) is still at 252kHz. Radio 4 still broadcasts at 198kHz , and incidentally sends a sideband that controls Britain's electricity meters. Don't tell the Russians! Terrible quality. Must need a huge aerial really.
Mustn't go on. Just had a listen to Thomas Dolby "The Golden Age of Wireless". Still sounds fresh.
Attachments
I did say that it was a "crystal" earpiece in the radio kit, which is a type of piezoelectric earphone.
The headphone unit I used as a boy was as you describe, and as shown in Step 2 of this link: Vintage Wartime Radio Headphones : 7 Steps - Instructables
The English programmes of Radio Luxembourg moved on 2 July 1951, from long wave to the medium wave frequency of 208 metres (1439 kHz).
"208 - Your station of the stars" or, as I called it, "208 - My station on the stairs"! 😀
Quite right, Galu. And it seems a popular show at 18.15 on Sunday in 1952 was "The Ovaltiney's Concert Party". Sponsored by Ovaltine.
Ovaltineys-We Are The Ovaltineys.wmv - YouTube
Nothing except Church was open in those days. So it is likely my 13-y-o sister was listening.
She'd often burst into a cheerful song whilst making sponge mixture or such later in my youth:
"We are the Ovaltiney's, Little Girls and Boys...
... Because we all drink Ovaltine, We're happy girls and boys!"
Now I know!
All Radio people know that the characteristic impedance of Free Space Z nought is 377 Ohms. The (unrelated) impedance of a half-wave dipole is 73 Ohms plus 43 Ohms inductance, but most FM radios come with a folded dipole around 292 Ohms.
What they usually don't know, is that the Fine Structure Constant, alpha or 1/137 is related to this.
Alpha = (e^2 x Z nought ) / 4 Pi x h bar.
An interesting mix of classical and quantum physics. e being the electron charge. 😎
Ovaltineys-We Are The Ovaltineys.wmv - YouTube
Nothing except Church was open in those days. So it is likely my 13-y-o sister was listening.
She'd often burst into a cheerful song whilst making sponge mixture or such later in my youth:
"We are the Ovaltiney's, Little Girls and Boys...
... Because we all drink Ovaltine, We're happy girls and boys!"
Now I know!
All Radio people know that the characteristic impedance of Free Space Z nought is 377 Ohms. The (unrelated) impedance of a half-wave dipole is 73 Ohms plus 43 Ohms inductance, but most FM radios come with a folded dipole around 292 Ohms.
What they usually don't know, is that the Fine Structure Constant, alpha or 1/137 is related to this.
Alpha = (e^2 x Z nought ) / 4 Pi x h bar.
An interesting mix of classical and quantum physics. e being the electron charge. 😎
Attachments
For my antenna, I climbed onto our roof (South Africa, ‘double story’ house) and ran a copper wire across it.
Not a particularly good idea, because lightening storms were a very regular occurrence in the summer.
Talking about doing stupid things, don’t get me started on my naphthalene and permanganate of potash (KMnO4) rocket fuel . . .
Not a particularly good idea, because lightening storms were a very regular occurrence in the summer.
Talking about doing stupid things, don’t get me started on my naphthalene and permanganate of potash (KMnO4) rocket fuel . . .
I remember the song well!
Someone commented that nowadays they would be singing "We are the Quarantineys"! 😱
P.S. -
- how did that rampant apostrophe get in there Steve? Surely you're old enough to have had an EDUKASHION! 😀
P.P.S. You're a gambling man, Steve, but perhaps you are too young to remember Horace Batchelor on Radio Luxembourg touting his "Famous Infra-Draw Method" which he claimed would increase your chances of winning the Football Pools.
Members here will reveal their age if they remember how Horace made clear his address: "Keynsham, spelt K-E-Y-N-S-H-A-M".
Last edited:
I think Ovaltiney preserves the product name. Otherwise it would be Ovaltinies. Dunno.
I know KEYNSHAM, Galu, been there. Bought the Album.
Narrow miss on the Horses today. TBH, I just called in to find out from Ruthie if the Boxing Guy had won his huge Furey in the 7th. round bet. No, Furey won in the 11th! Decided to just pick a horse whose name I liked. Went for "Wee Pablo" at 9-1 in the 4.15 at the Curragh. I never spotted the winner down the list with my glasses steamed up from my facemask. "Avagardner". 80-1! Darn, I used to live round the corner from her. 😡
It never occurred to me to try Potassium Permanganate as a Rocket oxidant! And I had a huge tub of it. 😡
Smelly Napthalene was made from Coal Tar. Mothball stuff, and used in soap to kill nits and germs. Everybody remembers the smell of Coal Tar Soap. Still like it.
I was trying to remember what I power my bath toy cardboard boats with. It was similar Camphor. It worked!
Camphor boat (Marangoni effect) - YouTube
The British and Chinese had a war in 1868 over the supply of this useful stuff. 😕
Back to Physics. Recall in the Standard Model, the Boffins fix any problems by inventing a new particle?
The String Theorists are just as bad. They keep adding more dimensions. The latest wheeze is to have TWO dimensions of time in String Theory and M-Theory to explain the quantum. Might work, actually. We are now up to 11 or 12 dimensions. Not sure.
There are 2 dimensions of time, theoretical physicist states - Big Think
F-theory - Wikipedia
I believe it all works on a 2-Torus, aka a Donut. Have started work on it.
I know KEYNSHAM, Galu, been there. Bought the Album.
Narrow miss on the Horses today. TBH, I just called in to find out from Ruthie if the Boxing Guy had won his huge Furey in the 7th. round bet. No, Furey won in the 11th! Decided to just pick a horse whose name I liked. Went for "Wee Pablo" at 9-1 in the 4.15 at the Curragh. I never spotted the winner down the list with my glasses steamed up from my facemask. "Avagardner". 80-1! Darn, I used to live round the corner from her. 😡
It never occurred to me to try Potassium Permanganate as a Rocket oxidant! And I had a huge tub of it. 😡
Smelly Napthalene was made from Coal Tar. Mothball stuff, and used in soap to kill nits and germs. Everybody remembers the smell of Coal Tar Soap. Still like it.
I was trying to remember what I power my bath toy cardboard boats with. It was similar Camphor. It worked!
Camphor boat (Marangoni effect) - YouTube
The British and Chinese had a war in 1868 over the supply of this useful stuff. 😕
Back to Physics. Recall in the Standard Model, the Boffins fix any problems by inventing a new particle?
The String Theorists are just as bad. They keep adding more dimensions. The latest wheeze is to have TWO dimensions of time in String Theory and M-Theory to explain the quantum. Might work, actually. We are now up to 11 or 12 dimensions. Not sure.
There are 2 dimensions of time, theoretical physicist states - Big Think
F-theory - Wikipedia
I believe it all works on a 2-Torus, aka a Donut. Have started work on it.
Attachments
I felt a reduction in tension upon watching that video, but I fear it was only on the surface! 😉
A drop of washing up liquid produces the same effect, if you want to try it folks.
The Soap Boat Experiment Teaches Alternative Energy | The Instillery
With Bars' two dimensions of time and the 10 dimensions already in m-theory, that would mean that we inhabit a 13 dimension universe.
Aren't we lucky! 😀
I am off to bed now. But am pretty sure F-Theory gives 12 dimensions. 4 Space-Time, 6 Calabi-Yau compactified Space ones. One for Ed Witten's M-Theory which is a Brane or something, and an extra (compactified?) time dimension.
M-Theory: The Mother of all SuperStrings : Official Website of Dr. Michio Kaku
Must be true, IMO. 12 is a much more interesting number than 11 or 13. Everybody happy? 😱
...stumbles off to bed, hopefully dreaming of an 80-1 winner in my next race....
Michio Kaku said:
M-Theory: The Mother of all SuperStrings : Official Website of Dr. Michio Kaku
Must be true, IMO. 12 is a much more interesting number than 11 or 13. Everybody happy? 😱
...stumbles off to bed, hopefully dreaming of an 80-1 winner in my next race....
- Status
- Not open for further replies.